DEGs in transcriptome of virulent CN-Bx1 and avirulent US-Bx1. from Enhancement of oxidative stress contributes to increased pathogenicity of the invasive pine wood nematode

Reactive oxygen species (ROS) play important roles in defence response of host plants versus pathogens. While generation and detoxification of ROS is well understood, how varied ability of different isolates of pathogens to overcome host ROS, or ROS contribution to a particular isolate's pathogenicity, remains largely unexplored. Here, we report that transcriptional regulation of ROS pathway, in combination with the insulin pathway, increases the pathogenicity of invasive species <i>Bursaphelenchus xylophilus</i>. The results showed a positive correlation between fecundity and pathogenicity of different nematode isolates. The virulent isolates from introduced populations in Japan, China and Europe had significantly higher fecundity than native avirulent isolates from the USA. Increased expression of <i>Mn-SOD</i> and reduced expression of <i>catalase</i>/<i>GPX-5</i> and H₂O₂ accumulation during invasion are associated with virulent strains. Additional H₂O₂ could improve fecundity of <i>B. xylophilus</i>. Furthermore, depletion of <i>Mn-SOD</i> decreased fecundity and virulence of <i>B. xylophilus</i>, while insulin pathway is significantly affected. Thus, we propose that destructive pathogenicity of <i>B. xylophilus</i> to pines is partly due to upregulated fecundity modulated by insulin pathway in association with ROS pathway and further enhanced by H₂O₂ oxidative stress. These findings provide a better understanding of pathogenic mechanisms in plant–pathogen interactions and adaptive evolution of invasive species.This article is part of the theme issue ‘Biotic signalling sheds light on smart pest management’.